1. Field of the Invention
This invention relates to a variable capacity wobble plate compressor.
2. Description of the Prior Art
A variable capacity wobble plate compressor includes a thrust flange rigidly fitted on a drive shaft, a drive hub mounted on the drive shaft via a hinge ball which is a slidable along the drive shaft, and a link arm connecting one radial end portion of the thrust flange and one radial end portion of the drive hub to each other.
The thrust flange, the drive hub, and the link arm form a linkage, which transmits torque of the drive shaft from the thrust flange to the drive hub via the link arm.
The link arm has one end thereof pivotally connected to the one radial end portion of the thrust flange by a front link pin, and the other end thereof pivotally connected to the one radial end portion of the drive hub by a link pin.
FIG. 1 shows construction of the linkage of the conventional variable capacity wobble plate compressor in detail in cross section.
A thrust flange 240 has one radial end portion thereof formed with a pair of arm-holding portions 245, 246 axially extending inward in parallel with each other.
The link arm 242 is comprised of a first link arm 242A arranged in a manner sandwiched between an inner surface of the arm-holding portion 245 and one side face of a protruding portion 247 of the drive hub 241, and a second link arm 242B arranged in a manner sandwiched between an inner surface of the arm-holding portion 246 and the other side face of the protruding portion 247 of the drive hub 241.
The link arm 242 is assembled with the thrust flange 240 by press-fitting the front link pin 243 in a direction indicated by arrow "a" via through holes 246a, 242b, 242a, and 245a which are formed through the arm-holding portion 246, the second link arm 242B, the first link arm 242A, and the arm-holding portion 245, respectively.
After the press-fitting of the front link pin 243 is completed, a retaining ring 243a is fitted on an end of the front link pin 243 so as to retain the pin 243.
However, in the variable capacity wobble plate compressor having the linkage constructed as above, when a clearance between the inner surface of the arm-holding portion 245 and the first link arm 242A and a clearance between the inner surface of the arm-holding portion 246 and the second link arm 242B are excessively large, large noise is produced due to vibrations caused by operation of the compressor, and further, for example, the root of the drive hub 241 can be broken due to impact load resulting from gaps produced between respective end portions of the arm-holding portions 245, 246 and the link arms 242A, 242B (lowered reliability of the compressor).
Inversely, when the clearance between the inner surface of the arm-holding portion 245 and the first link arm 242A and the clearance between the inner surface of the arm-holding portion 246 and the second link arm 242B are excessively small, the drive hub 241 cannot move smoothly, which results in degradation of controllability of the compressor.
To overcome these problems, it is required to hold constant the clearance between the inner surface of the arm-holding portion 245 and the first link arm 242A and the clearance between the inner surface of the arm-holding portion 246 and the second link arm 242B.
In the conventional linkage, however, the above-mentioned tolerances are so close compared with machining tolerances of the drive hub 241 and the thrust flange 240 that it is necessary to have a stock of tens of types of link arms which are different in thickness from each other and select from the stock a pair of link arms each having a thickness conforming to the above-mentioned clearances when each linkage is assembled.
Further, since the front link pin 243 is fitted in by press-fitting as described above, the distance between the inner surfaces of the arm-holding portions 245, 246 (and hence each of the above-mentioned clearance) is decreased. To overcome this problem, it is required to adjust the distance between the inner surfaces of the arm-holding portions 245, 246 after the press-fitting by applying a predetermined pressure to the press-fitted front link pin 243 in a direction (indicated by arrow "b") opposite to the press-fitting direction.
Moreover, a gap exists between the arm-holding portion 245 and the retaining ring 243a, so that when the compressor is operation, a force developed in a direction of increasing the distance between the opposed inner surfaces of the arm-holding portions 245, 246 can expand the distance between the arm-holding portions 245, 246 against frictional forces acting respectively between the arm-holding portions 245, 246 and the front link pin 243 to deform the thrust flange 240, which hinders reduction of noise due to vibrations and impairs reliability of the compressor.